I honestly believe long skirts are better and cuter than short skirts.
That's ankle length. Below the knees is for proper ladies.
Knee length best length
I don't dislike mini-skirts, but I feel anime overdoes them these days. I understand why ecchi anime would have them so short, but even cleaner anime do it. It'd be nice to see a little variety here and there.
I can appreciate a good miniskirt now and then but I generally think girls look prettier in longer skirts and dresses.